In 2001, Zhang et al., Circulation, 104:832-838 (2001), the disclosure of which is incorporated by reference, described a phenomenon termed “His electrogram alternans,” or “HE alternans.” It was observed that by recording HE alternans, the clinician may visualize atrioventricular (AV) nodal dual pathway conduction. In addition to Zhang, supra, see Zhang, et al., Circulation, 107:1059-1065 (2003); Zhang, et al. Cardiovascular Research, 61:45-55 (2004); Zhan, et al., J. Cardiovasc. Electrophys., 22:1256-1262 (2011); Zhang, et al., Int. J. Cardiology, 171:259-264 (2014); and Zhang, et al., J. Interv. Card. Electrophysiol., 40:99-103 (2014); all of which are incorporated by reference.
The concept of dual pathway AV node electrophysiology was developed, initially, to explain AV nodal re-entrant tachycardia (AVNRT), which is the most common type of paroxysmal supraventricular tachycardia. Prior to the observation described supra, also called Zhang's Phenomenon, there were no tools or values available which could be used to monitor dual pathway conduction with the exception of a “sudden jump” in the AV node conduction curve. This “sudden jump” was defined as a sudden increase of AV conduction time, of 50 mseconds (ms) or more with premature beats shortened in 10 ms steps. While it was believed that this sudden jump resulted from a switch of AV conduction from fast to slow pathway conduction, not every patient was, or is, seen to exhibit this jump. An additional issue is that this jump is only revealed when the whole AV conduction curve is studied. No methodologies were available, before the discovery of Zhang's phenomenon, to monitor dual pathway AVN conduction on a beat-by-beat basis. Prior to the invention, dedicated means for determining it were not available. It is now believed that dual pathway AV node conduction may exist in all patients, and determining HE alternans can be used in routine clinical cardiac electrophysiology in order to monitor dual pathway AV conduction. The phenomenon is especially useful during catheter ablation of atrioventricular nodal reentrant tachycardia, or any AV node modification approach involving dual pathway AVN conduction, including AVN modification to slow ventricular rates during atrial fibrillation.
At present, His electrogram recording is done, routinely, during clinical cardiac electrophysiology examination. It is only used as a marker of electrical excitation reaching the His bundle. In other words, it is used to measure AV conduction time intervals, and His ventricular intervals. It is not used as an index of dual pathway AV nodal conduction.
It is a purpose of this invention to facilitate the measurement of this phenomenon by way of an easily manufactured, easily used device.
The medical arts are replete with various catheter probes which are used either to receive information from tissue, such as cardiac tissue, or to deliver signals, such as electrical charges. An exemplary, but by no means exhaustive list of references showing various embodiments of catheters includes EP 499 491; U.S. Pat. No. 4,649,924; PCT/US94/03768; U.S. Pat. Nos. 4,974,588; 5,063,932; 5,184,620; 8,777,851; Published U.S. Patent Application 2014/0128935, and Published U.S. Patent Application 2012/0108993.
Even a cursory review of this sampling of the literature will show that for catheters “form follows function.” In other words, the shape of the catheter, including the catheter tip or probe, and the extended member which leads to the tip or probe, will change, depending upon the intended function of the catheter. Similarly, while all of these catheters incorporate electric poles, some, such as pace maker type devices are designed to discharge an electrical signal, while others include poles which receive and transmit an electrical signal.
Typically, electrophysiology catheters have essentially the same form, with a body, “tail,” and “tip,” as is shown in FIG. 1. To the extent that these “EP” catheters differ, they differ in the tip. FIG. 2a shows various types of prior art tips, and FIG. 2b, “ring type” electrodes, which are common.
In order to carry out functions as described herein, a catheter must be designed such that it can be placed in a blood vessel, e.g., a vein or an artery, which leads to cardiac tissue, such as cardiac muscle, the His bundle in particular. Further, the catheter tip or probe must be designed to fit precisely on the targeted cardiac tissue, i.e., the His bundle.
As will be shown in the disclosure which follows, the inventor has developed a catheter means which fulfills the requirements discussed supra. The details thereof will be elaborated upon in the disclosure which follows.